The purpose of this program is to explore the possibility that a new class of synthetic polymers, the poly(organophosphazenes), can be utilized in three areas of biomedicine: (1) as non-thrombogenic materials for the replacement of tissues, especially in devices incorporated into the circulatory system; (2) as carrier macromolecules for the controlled, targeted delivery of chemotherapeutic drugs; and (3) as immobilization substrates for enzymes, cells, affinity components, or redox species. The recent work has opened up synthetic routes to the binding of drugs such as steroids, sulfa drugs, or dopamine to polyphosphazenes that will decompose at body pH to harmless small molecules with concurrent release of the active drug molecules. In the forthcoming work we hope to expand the scope of this route for the controlled release of a wider range of drug molecules. Also planned is the development of methods for the attachment of heparin and other non-thrombogenic species to polymers that may be of value in artificial organ research. In addition, the linkage of enzymes, affinity substrates, and metalloporphyrins to polyphosphazenes will be explored.